Operative viva Flashcards
Talk me through the approach to an anterior circulation aneurysm.
In an appropriately consented patient under GA, I would place the patient supine on the operative table with the head turned to the contralateral side in a Mayfield clamp. PCom = 30 deg MCA = 45 deg ACom 60 deg The malar eminence is at the highest point. Before starting I would ensure I have 1) a microscope available with ICG capability, 2) a Doppler probe and 3) an array of aneurysm clips available. Pterional incision from the zygoma to the widow’s peak behind the hair line. Reflection of a myocutaneous flap. Burr holes at McCarty’s keyhole and above the zygoma. Craniotomy. The greater wing of the sphenoid is drilled down until flush with the anterior cranial fossa floor. A myocutaneous flap is raised prior to a C-shaped durotomy Subfrontal retraction to identify the olfactory nerve, which is followed back to the optic nerve and carotid artery. I would allow CSF egress from the optico-cartoid cistern and then gain proximal control. The ICA can then be followed to the artery.
How do you perform a transcallosal approach for a colloid cyst?
In an appropriately consented patient under GA, I would place the patient supine on the operative table with the head neutral in a Mayfield clamp. I would raise the head of the bed to 30 deg. I would utilise image guidance to I perform a souttar incision and place burr holes on either side of the midline 4cm anterior to the coronal suture and 2 cm behind. The craniotomy is carried 5 cm lateral. The dura is reflected over the midline taking care to preserve any cortical and bridging veins. Interhemispheric sharp arachnoid dissection is performed and the calloso-marginal arteries and cingulate gyri are encountered at the bottom edge of the falx. The dissection is continued between the cingulate gyri to the corpus callosum. The pericallosal arteries are identified and a 2 cm transection of the callosum is performed. Orientation within the ventricle is achieved by following the choroid plexus and thalamostriate veins to the foramen of monroe. Transforaminal approach is preferred and can be expanded through the transchoroidal or interforniceal routes. The colloid cysts should be aspirated and released from the tela choroidae. Care should be taken to prevent release of the contents into the CSF potentially resulting in a chemical meningitis.
What syndrome is characterised by visual loss and opthalmoplegia?
Orbital apex syndrome
Describe a transphenoidal approach.
In an appropriately consented patient under GA, I would place the patient supine on the operative table with the head in a Mayfield clamp. I would rotate laterally flex the head at facilitate access to the nostrils. I would utilise neuronavigation. A lumbar drain is placed for macroadenomas with significant suprasellar extension or for extended cases. I would instil Moffatt’s solution (Cocaine 10% 1ml + Adrenaline 1ml 1:1000 + Bicarbonate. 2ml 8.4%) and prepare the abdomen or thigh for a fat graft. A direct endoscopic approach is performed with lateralisation of the middle turbinate and identification of the sphenoid ostium. A nasoseptal flap may be raised for extended procedures. The bony septum (vomer) is disarticulated from sphenoid rostrum. The sphenoid sinus is entered and the septations are removed. The optic nerve, OCR, carotid arteries and sellar are then identified. The sella then drilled and the dura opened in a cruciate fashion. Suction, angled ring curettes and biopsy forceps are used to deliver the tumour. Valsalva or aliquots of saline can be added to the lumbar drain to aid with delivering suprasellar portions.
What is Moffatt’s solution?
Moffatt’s solution = Cocaine 10% 1ml + Adrenaline 1ml 1:1000 + Bicarbonate. 2ml 8.4%
What are the complications of a transsphenoidal approach?
Epistaxis (sphenopalatine artery) CSF leak = rhinorrhea Sinusitis Visual impairment Addisonian crisis DI Endocrinopathy Meningitis Opthalmoplegia (Cavenous sinus) Carotid injury
Why is a CT helpful for transsphenoidal cases?
Neuronavigation Identify the nasal anatomy Identify the sellar type (sellar, pre-sellar and conchal) Sphenoid septations may lead to the carotid canal
What do headaches and visual deterioration suggest?
Raised ICP. This may be due to hydrocephalus, tumours, trauma, venous outflow obstruction etc
Describe an ETV.
In an appropriately consented patient under GA, I would place the patient supine on the operative table with the head in a Mayfield clamp. I would utilise neuronavigation and plan a trajectory from a pre-coronal burr hole 3cm from the midline passing through the foramen of monroe to the tuber cenereum in the midline. I would perform a C-shaped incision, single burr hole hole and insert a peel-away cathter (14 French) into the lateral ventricle. I would insert the rigid endoscope, obtain orientation within the ventricle utilising the choroid plexus, septum and thalamostriate veins guiding me to the foramen of monroe. I would fenestrate the floor of the third ventricle at the tuber cenerem between the mamillary bodies and the infundibular recess and dilate this using a 4Fr fogarty catheter with 0.2ml of air. I would advance the endoscope into the prepontine cistern and inspect for any remnant of Lillequists membrane. I would leave an EVD or access device if there was significant bleeding. I would then perform a biopsy of a lesion at this stage if required.
What are the imaging features indicative of hydrocephalus?
Evan’s ratio >0.3 (FH:BPD) Bicaudate ratio >0.25 FH:Internal skull dia ratio >0.5 Temporal horns 2 mm Ballooning of the third ventricle Thin / stretched CC Periventricular oedema Empty sella Dilated optic nerve sheath diameters
What is the ETV success score?
This is a predictive score of the failure rate of ETV (based on the likelihood of needing a VP shunt @6 month). Predictive factors include: Age (<1 month = 0, 1-6 months = 10, 6-12 months = 30, 1-10 years = 40 and >10 years = 50). Aetiology (Infection = 0, MMC/IVH/tumour = 20 and Aqueduct stenosis = 30). Previous infection (No = 10). Maximum score is 90%.
What is the cause of chronic neck pain and occipital headaches worse with coughing / sneezing / valsalva?
Chiari type 1 malformation
How would you perform an FMD?
In an appropriately consented patient under GA, I would place the patient prone on a Montreal mattress in the Concorde position with the head in a Mayfield clamp taking care to avoid overflexion and ensuring no obstruction to venous outflow. I would perform a linear incision from inion to C2 with bilateral muscle strip and exposure of the C1 lamina. I would perform a suboccipital craniectomy (3x3 cm) and potentially remove the arch of C1. Y-shaped opening of the dura. If this restores flow across the CCJ then I would perform an expansion duroplasty using autologous pericranium or a dural patch (DuraGuard = Bovine pericardium / DuraRepair = horse Achilles tendon) and multilayered closure. If the tonsils are very low and CSF across the CCJ is not restored then I would undertake tonsillopexy taking care to preserve the PICA.
What are the causes occipital headaches and numbness / tingling in the fingers? Long tract signs?
Syrinx and FM tumour / CCJ compression
What approach would you use for a ventrolateral foramen magnum meningioma?
Far lateral approach
In an appropriately consented patient under GA, I would place the patient in the park bench position on the operative table with the head in a Mayfield clamp. I would utilise neuronavigation and mark a mitre incision (inverted hockey stick) extending from C3 up to the inion in the midline, along the superior nuchal line to the tip of the mastoid process.
The myocutaneous flap would be elevated and retracted inferiorly and laterally.
The C1 lamina, vertebral artery and lateral mass are identified. The foramen magum is opened.
The vertebral artery can be transposed to facilitate drilling of the occipital condyle (<1/3) to prevent instability.
Curvilinear dural opening.
How do you perform a middle fossa approach? e.g. to a petroclival meningioma
Subtemporal transtentorial approach
In an appropriately consented patient under GA, I would place the patient in the park bench position on the operative table with the head elevated 30 deg in a Mayfield clamp. I would utilise neuronavigation and mark an incision from zygoma to 2 cm behind the mastoid curving posteriorly over the pinna.
A low temporal cranitiomy is performed at the floor of the temporal fossa.
Extradural dissection is peformed with coagulation of the MMA, peeling from posterior to anterior to prevent traction on the GSPN.
The arcuate eminance is identified and driling of Kawase’s triangle is performed.
The dura is opened in a T-shape with one limb parallel to the inferior temporal lobe and the other perpendicular along the floor of the temporal fossa.
The CN4 should be identified and protected prior to division of the Sup. Petrosal Sinus.
How would you perform a retrosigmoid approach?
In an appropriately consented patient under GA, I would place the patient in the park bench position on the operative table with the head elevated 30 deg in a Mayfield clamp.
I would perform a curvilinear incision 2 finger-breadths behind the ear and place a burr hole 1cm medial and inferior to the asterion.
I would reflect the dural leaflets over the transverse and sigmoid sinuses.
I would drain CSF to relax the cerebellum and then gently place a fixed retractor on the superior surface of the cerebellum (for TN MVD) or lateral cerebellum for VS / HFS MVD. Further CSF can be drained from the foramen magnum.
I would be mindful to prevent avulsion of Dandy’s vein (aka superior petrosal vein).
What is the safest way to identify and preserve the CN7/8 with large VS?
Identify the nerves at the exit from the brainstem and roll the tumour laterally.
Label the anatomy of the CP angle.
How is facial nerve monitoring performed during Vestibular Schwannoma surgery?
EMG electrodes are placed in the orbicularis oculi and oris muscles as well as a ground electrode on the forehead.
Free running EMG and direct stimulation is performed.
A concentric bipolar electrode probe is used starting with a stimulation intensity of 0.05 mA building up in 0.02 mA steps until a response is received. Square wave pulse at 5Hz.
Elevation of stimulation >0.3mA correlates with a poor post-operative facial nerve function.
How are brainstem auditory evoked potentials recorded?
An ear mould is placed in the ipsilateral EAC to deliver click noises.
The responses are measured by electrode montages from A1 (anterior to the tragus) with bipolar montage to Cz.
Responses = ECOLI!!
How do you perform an ACDF?
In an appropriately consented patient under GA, I would place the patient supine on the operative table with the head on a ring. I would place a roll under the neck/shoulders taking care not to hyperextend the neck and I would tape the chin and shoulders.
I undertake a pre-operative xray for level marking and perform a transverse skin crease incision.
I raise a subplatysmal flap and continue my dissection at the medial border of SCM identifying the carotid sheath and retracting it laterally.
Omohyoid may be encountered and can be mobilised or divided as required
The prevertebral fascia is opened longitudinally and longus coli are retracted laterally.
Caspar pins are inserted under II guidance and distracted. A superficial discectomy is peformed with a currettes using the uncovertebral joints as the lateral margins.
Posterior osteophytes are removed with a high speed drill and the PLL is opened to reveal the dura.
The cartilagenous endplates are removed and a cage with bone graft (autologous from osteophytes or synthetic) is inserted (14 mm depth and 14-18 mm width).
The retractors are removed and a drain is placed on gravity.
What are the complications of an ACDF?
Bleeding - neck haematoma / airway obstruction
Infection - potentially requiring hardware removal
Hoarse voice - recurrent laryngeal nerve palsy (20% transient, 4% permanent)
Dysphagia
Oesophagal injury
Tracheal injury
Horner’s syndrome
Spinal cord or root injury injury - Paralysis, bowel / bladder dysfunction, sensory loss and loss of hand function
Delayed C5 root palsy
Adjacent level disease
Hardware failure / subsidence / failure to fuse
What proportion of disc prolapses occurs in the thoracic spine?
<1%
Where are thoracic disc prolapses most likely to occur?
Below T8 (as the thoracic spine is more mobile)
What is the most common site for a thoracic disc prolapse?
T11/12
How would you investigate a thoracic disc prolapse?
MRI
CT - as frequently calcified (2/3)
**Always use IONM**
What are the approaches to thoracic disc prolapses
- Costotransversectomy
- Lateral extracavitatory (retropleural)
- Transthoracic approach - has the best operative results and lowest results of injury. Left sided approach avoids the SVC / IVC and hemiazygous / azygous. Right sided approach avoids the artery of Adamkiewicz, heart and aorta.
What does a costotransversectomy involve?
Resection of the TP and 5 cm of rib.
Disruption of the segmental / spinal artery results in cord ischaemia!
Risk of pneumothorax.
Where does the artery of Adamkiewicz arise?
Between T8-L1 and from the left side in 80%.
Describe a transthoracic approach to a discectomy.
After consent and GA with a double-lumen ET tube, the patient is placed in a lateral position with the right side up (unless it is low thoracic then use the left side as the IVC is difficult to mobilise on the right).
Intraoperative neurophysiological monitoring would be instituted throughout the case.
Lateral Xray for level check (as a radiologist to put cement into the VB below)
A thoracic surgeon is employed to aid with the approach. A rib is resected (one or two above the disc for removal to allow direct lateral access to the disc), pleura opened and the lung is deflated.
The intercostal neurovascular bundle is used to guide the surgeon to the neural foramen.
Trenches are drilled into the posterior VB above and below the disc. The disc is then dissected into the trench away from the cord without manipulating the cord.
The rib can be used as an autologous bone graft and a plate is placed between the VBs.
What is the difference between a transthoracic and retropleural approach?
The retropleural approach does not open the parietal pleura and retracts the parietal pleural forwards after opening the endothoracic fascia giving the same access as a transthoracic approach.
A chest drain is needed for a transthoracic approach as both the parietal and visceral pleura are opened. For a retropleural approach in which only the endothoracic fascia is opened then only a wound drain is placed.
How do you perform a far lateral discectomy?
In an appropriately consented and anaesthetised patient, I would position them prone on the Montreal mattress and undertake an x-ray for the level check.
I would utilise a Wiltse approach and make a paramedian incision on the ipsilateral side 3 cm from the midline. I would find the intervening fascia between multifidus and longissimus and dissect down the plane to the facet joint and TP.
Internal xray is used to confirm the level again.
The intertransverse ligament is incised and using a microscope the neural foramen is identified with the exiting nerve root underneath the pars.
Label the thoracic vertebra
Label the lumbar vertebra
How do you perform a lumbar pedicle screw fixation?
Pre-operatively I would measure the diameter and length of the screws on the CT.
I would then position an appropriately consented and anaesthetised patient prone on a montreal mattress and undertake an external level check prior to a midline incision and bilateral muscles strip. I take another internal Xray for level check and identify the superior articular facet, the pars and the TP to identify the screw entry point.
I would then used a sharp awl and pedicle finder and place the screw.
Medial lateral angulation is based on the level increasing at 5 deg interval from L1 = 5 deg, L2 = 10 deg, L3 = 15 deg, L4 = 20 deg, L5 = 25 deg and S1 = 30 deg.
The facet joints are decorticated and bone graft is placed in the gutters. Autologous bone graft or synthetic (DBX = demineralised bone matrix from cadaveric source)
The screws are connected to rods and final tightened.
What is a lumbar infusion study?
Used to investigate NPH and shunt valve function and is based on the principle that the CSF absorption rate varies with ICP.
One or two needles are inserted into the CSF space and the CSF pressure is measured as the baseline in the lateral decubitus position.
Hartmann’s solution is infused at a steady rate starting at 1ml/min through one needle and the pressure is measured constantly through the other needle until a steady-state plateau pressure is achieved (at least 45 minutes). This indicates the pressure level at which the absorption rate is equal to the infusion rate.
A resistance to infusion (R out) >18 mmHg/ml/min is indicative of shunt response in NPH. If testing shunt function, the peak pressure is the opening pressure of the valve.
How do you perform a percutaneous trigeminal rhizotomy?
The symptomatic side is marked and the patient is placed under GA with an LMA in a supine position.
Hartel’s technique is used to anatomically place the needle into the foramen of Ovale with an entry point 2.5 cm from the corner of the mouth aiming for a target point at the intersection of lines at the mid pupillary line and a point 3 cm anterior to the tragus.
Local anaesthesia in placed into the cheek and a finger is placed into the mouth to prevent transgression of the oral mucosa.
To confirm the position, CSF is liberated and 1 ml of Iodinated water-soluble contrast agent (Iohexol) can be used to perform trigeminal cisternography.
During RF ablation the patient is woken up and then stimulation is performed to reproduce the pain.
What RF stimulation settings do you use?
0.2-0.6V aiming for a probe temperature of 70 deg for 60 seconds.
High stimulation settings >0.8V mean the needle needs repositioning.
After the RF ablation, the patient is woken up and the amount of anaesthesia in the V1-3 is measured. The ablation is repeated after repositioning if sufficient hypoaesthesia is not achieved.
What are the complications associated with poor needle placement?
- Carotid injury / intracavernous injury
- IOF (Blindness and opthalmoplegia)
- Jugular foramen (Lower cranial nerve injury)
What do you aim on xray for the different trigeminal divisions during a percutaneous ablation procedure?
5 mm below the sella = V1
10 mm below the sella = V2
15 mm below the sell = V3
What are the components of a shunt valve?
There is a differential pressure unit and a gravitational unit.
The differential pressure can be fixed or adjustable and when the CSF pressure rises above the set pressure the valve opens and CSF drains. The mechanism usually involves a ruby with the pressure being dependent on a spring. Other designs involve silicon mitre, silicon slit valves and rubber diaphragm valves. There are also flow regulated devices.
The gravitational unit can be fixed or adjustable and engages when the patient is upright to prevent a siphoning effect.
How do flow regulated valves work?
They demonstrate a sigmoidal relation between pressure and flow by maintaining a fixed aperture through which CSF can flow meaning the flow remains relatively constant over a certain pressure range. Beyond maximum pressure, the maximum flow is reached and does not increase any further. The maximum flow is based on Poiseulle’s law where the flow is proportional to the radius^4.
The orbis sigma is one example and is useful when patients are volume drainage dependent and at risk of overdrainage.
Where do the anterior and posterior ethmoidal arteries enter the skull?
The anterior and posterior ethmoidal arteries are branches of the ophthalmic arteries and enter the skull as the junction of the cribiform plate (ethmoid bone) with the frontal bone.
How do you decompress the optic nerves through a subfrontal approach?
The falciform ligament which forms the roof the optic canal and is continuous with the distal dural ring is incised and released.
Label the anatomy of the sphenoid bone
Describe the VFD
There is a bitemporal hemianopic defect which is also involving the inferior nasal quadrants bilaterally. This suggests that the compression is worse on top of the chiasm and is in keeping with a suprasellar mass pushing down on the chiasm and not a sellar mass pushing up. This would be consistent with a tuberculum sella meningioma.
How do you deal with a parasagittal meningioma involving the sinus?
The Sindou classification separates these into those in which the meningioma involves the outer dura, infiltrate the sinus and completely occlude the sinus.
Dedicated venous imaging is needed to assess the patency of the venous sinus and identification of cortical venous collaterals.
In the case of involvement of the outer dura it may be possible to dissect this free. In cases of complete occlusion, it may be safe to sacrifice the sinus as venous collateralisation is likely to have occurred. For incomplete occlusion types, I would leave the sinus component and monitor this or treat it with SRS as appropriate.
What are the corridors to the 3rd ventricle?
Trans-foramen of monre
Transchoroidal (between the choroid plexus and fornix - taenia fornices)
Interforniceal (split the septum pellucidum)
How would you approach this lesion?
I would place an appropriately consented patient under general anaesthesia in a Mayfield clamp supine with the head neutral.
I utilise neuronavigation to plan a craniotomy straddling the superior sagittal sinus at the level of the coronal suture. I would utilise a bicoronal (Soutar incision) and aim to place burr holes on either side of the midline and extending 5 cm laterally on the right side.
I would then reflect the dural over the superior sagittal sinus and introduce the surgical microscope to undertake an interhemispheric transcallosal approach to the right ventricle. Once in the ventricle, I would orientate myself using the thalamostriate and septal veins as well as the choroid plexus and identify the foramen of Monroe, but this may be obscured by the lesion. If possible I would want to devascularise the lesion at the attachment to the choroid plexus as the vascular supply is from the anastomosis of the choroidal arteries.
I would then debulk the lesion using a CUSA and resect the lesion in total.
I would leave an EVD in situ for 24 hours.
Talk me through the principles of resecting this lesion.
The appearances are that of a midthoracic intradural extra-axial lesion arising from the ventral dura with broad dural attachment and is in keeping with a meningioma, but other possibilities include peripheral nerve sheath tumours (schwannomas and neurofibromas). This is a challenging case this represents a watershed area of the spine, the spinal cord is severely compressed and the lesion is ventral with the spinal cord draped over the back so impeding a direct posterior approach.
I would utilise intraoperative neurophysiological monitoring with SEEPs and MEPs ensuring my anaesthetist did not give any long-acting paralytics. or halogenated anaesthetics.
I would then take an appropriately consented and anaesthetised patient and position them prone on a montreal mattress. I would then gain an external level check through needle markings counting from the sacrum followed by fluoroscopy to reconfirm the levels.
I would perform a midline thoracic incision and bilateral muscle strip. I would undertake an internal level check and perform a laminoplasty of the lamina above and below the lesion.
In this case, there appears to be spinal cord on the dorsal surface making a posterior particularly challenging. A costrotransversectomy with drilling of the pedicles may also be required to facilitate access.
I would then undertake an ultrasound before opening the dura.
I would open the dura in the midline and hitch the leaves bilaterally. I would identify the superior and inferior margins. Thoracic nerve root sacrifice and release of the dentate ligament is required to facilitate gentle rotation of the cord. Resection is with a CUSA to debulk prior to capsule resection.
After resection of the lesion attention should then be paid to reconstruction of the dura if this is to be resected. The risk of recurrence is significantly higher if this is the case. A lumbar drain should also be left in situ for 5 days.
What are the principles of aneurysm surgery?
Positioning - to aid with gravity retraction of the brain and facilitate direct access to the aneurysm as well as for proximal control. Care is taken to prevent kinking of the neck veins which would result in venous congestion.
Craniotomy - should be large enough to allow access for proximal control, to the aneurysm, to allow for brain swelling in ruptured cases and potential post-operative swelling. The sphenoid wing should be drilled flat to minimise brain retraction.
CSF drainage - shoulder be performed early to allow adequate brain relaxation along with liberal arachnoid dissection. This can be performed through an EVD if present or after the craniotomy via Paine’s point.
Superficial clot evacuation would aid with brain relaxation.
Retractors - should be used to hold the brain and not to apply undue force.
Proximal control - and occlusion with a temporary clip in case of rupture is
essential.
Clipping - avoid perforator and distal vessel occlusion e.g. Heubner
Intraoperative doppler / ICG are useful to confirm exclusion of the aneurysm from the circulation as well as patency and flow in the distal branches.
Interpret the audiogram
There is a right-sided sensorineural hearing deficit as there is no difference between air and bone conduction.
Masking has been employed when testing the air and bone conduction to prevent crossover of sound from one ear to the other. Masked bone conduction has also been applied.
Masking is performed by applying noise to the non-test ear.
What is this lesion?
Pilocytic astrocytoma - most commonly in the cerebellar hemisphere. FLAIR shows a cystic lesion with a mural nodule. No surrounding oedema. Mass effect on the 4th ventricle results in obstructive hydrocephalus.
The differential would include a haemangioblastoma, medulloblastoma, ependymoma and ganglioglioma.
What is this lesion?
CT axial image through the posterior fossa shows a solid and cystic mass causing obstructive hydrocephalus. There is supratentorial hydrocephalusus. The isodensity of the solid component is in keeping with a pilocytic astrocytoma. I would expect medulloblastomas to be more hyperdense.
What is this lesion?
A hypothalamic / optic pathway glioma.
Coronal T2: This is a large lesion with no surrounding oedema.
1/3 of patients with OPGs have NF1.
Differential includes a pilomyxoid astrocytoma, ADEM, tumefactive MS, hypothalamic hamartoma.
What are these tumours in a child?
Supratentorial cyst with an enhancing nodule in a child is most likely a pilocytic astrocytoma. Other differentials include PXA, ganglioglioma (cortical and enhances) and DNET (no enhancement)
What is this lesion?
OPG - the enhancement pattern is variable. 1/3 of patients will have NF1.
What is this lesion?
The T2 image reveals a large H-shaped mass centred on the hypothalamus/chiasmatic region. It is well circumscribed with no oedema. The diagnosis is a pilomyxoid astrocytoma. The differential is an OPG (pilocytic astrocytoma) or craniopharyngioma.
What is the histology?
There are bipolar pilocytic cells wth no Rosenthal fibres.
There is mucin stain (blue) showing a mucinous matrix with embedded glial cells.
This is a pilomyxoid astrocytoma.
What is this lesion?
PXA (WHO grade 2) - these arise from SUBPIAL ASTROCYTES
A cortical lesion with solid contrast enhancing component in a child. Cystic component displacing the brainstem.
The histological section reveals nuclear pleomorphism with multinucleated giant cells and vacuolation.
What is this lesion in a child?
The CT shows a contrast enhancing lesion with in the latearl ventricle adjacent to the foramen of Monroe causing entrapment of the left lateral ventricle as evidenced by the ventriculomegaly and periventricular oedema. There is an associated hypodensity which most likely represents a cortical tuber.
The FLAIR confirms a complex heterogenous lesion at the forame of Monroe. There is a left posterior temporal cortical tuber and right frontal subcortical hyperintensity indicative of a focal cortical dysplasia. The child has tuberous sclerosis.
Differential includes a central neurocytoma, intraventricular meningioma, choroid plexus papilloma, astrocytoma arising from the septum pellucidum and an ATRT.
What are the imaging characteristics of oligodendrogliomas?
Cortical subcortical lesions that are heterogenous with solid and cystic components. There is deep infiltration and calvarial remodelling may occur. 90% show calcification on CT.
FLAIR shows significant surrounding oedema with cortical and subcortical involvement.
T1WI shows heterogenous enhancement.
What is this lesion?
Age 20-40 years
Well circumscribed lesion arising from the septum pellucidum causing compression of the foramen of Monroe bilaterally.
The MRI shows prominent flow voids and diffuse heterogeneous enhancement.
Differential includes a meningioma, SEGA, choroid plexus papilloma and astrocytoma.
